This invention relates generally to the fields of optical modulators, light valves, electro-optic filters, projection and flat panel display devices. More specifically, this invention relates to an all solid-state light valve, optical modulating device or optical filter that uses color-selective absorption at a metal-dielectric interface by surface plasmons.
In xe2x80x9cVoltage-Induced Color-Selective Absorption with Surface Plasmons,xe2x80x9d Applied Physics Letters, Volume 67, No. 19, Nov. 6, 1995, pp. 2759-2761, Yu Wang reported on the phenomenon of voltage-induced color-selective absorption at a metal/liquid crystal interface with surface plasmons. The surface plasmon, a collective excitation of electrons, absorbs all incident light at the resonance frequency of the plasmon. When incident p-polarized light is absorbed at the surface plasmon resonance, the reflected light shows the complementary color.
Wang teaches that by using a liquid crystal, whose dielectric constant varies with applied voltage, one can change the resonance frequency of the surface plasmon, which in turn provides a concomitant change in absorption. Changing the dielectric constant of the liquid crystal through the application of voltage results in the reflected light showing a color change.
FIG. 1 schematically shows the prior art as taught by Wang. In this figure, the projection display 10 includes a substrate 11, bottom electrode 12, alignment layers 13, spacers 14, top electrode 15, liquid crystal 16 and seal 17. Alignment layers 13, typically formed by deposition of a polyimide layer and mechanical rubbing of the surface, must be employed to impart a preferred direction to the liquid crystal 16. Spacers 14 are required to set the desired spacing between top electrode 15 and bottom electrode 12. Seal 17 is required to contain liquid crystal 16 between top electrode 15 and bottom electrode 12.
In U.S. Pat. No. 5,570,139, Wang describes a similarly designed liquid crystal embodiment and how this embodiment may be employed in projection display applications.
The invention relates to an all solid-state light valve and tunable filter that uses color-selective absorption at a metal-dielectric interface by surface plasmons. The solid-state surface plasmon light valve and tunable filter comprises a substrate, a bottom electrode, a solid-state electro-optic material, and a top electrode through which electromagnetic radiation may pass through and whose optical properties may be modified by suitable modulation of an electrical bias, i.e., an applied voltage between the top and bottom electrodes. The bottom electrode must be specifically fabricated using a refractory metal to allow the formation of the solid-state electro-optic material. Alignment layers, spacers, and seals are not required in this embodiment of the solid-state surface plasmon light valve and tunable filter.